Use TimeTicks for MediaSessionUmaHelper.

content/browser/media/session/media_session_uma_helper.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CONTENT_BROWSER_MEDIA_SESSION_MEDIA_SESSION_UMA_HELPER_H_
 #define CONTENT_BROWSER_MEDIA_SESSION_MEDIA_SESSION_UMA_HELPER_H_
 
 #include <memory>
 
 #include "base/time/clock.h"
 #include "content/common/content_export.h"
 
 namespace base {
-class Clock;
+class TickClock;
 }  // base namespace
 
 namespace content {
 
 class CONTENT_EXPORT MediaSessionUmaHelper {
  public:
   // This is used for UMA histogram (Media.Session.Suspended). New values should
   // be appended only and must be added before |Count|.
   enum class MediaSessionSuspendedSource {
     SystemTransient = 0,
     SystemPermanent = 1,
     UI = 2,
     CONTENT = 3,
     SystemTransientDuck = 4,
     Count // Leave at the end.
   };
 
   MediaSessionUmaHelper();
   ~MediaSessionUmaHelper();
 
   void RecordSessionSuspended(MediaSessionSuspendedSource source) const;
 
   // Record the result of calling the native requestAudioFocus().
   void RecordRequestAudioFocusResult(bool result) const;
 
   void OnSessionActive();
   void OnSessionSuspended();
   void OnSessionInactive();
 
-  void SetClockForTest(std::unique_ptr<base::Clock> testing_clock);
+  void SetClockForTest(std::unique_ptr<base::TickClock> testing_clock);
 
  private:
   base::TimeDelta total_active_time_;
-  base::Time current_active_time_;
-  std::unique_ptr<base::Clock> clock_;
+  base::TimeTicks current_active_time_;
+  std::unique_ptr<base::TickClock> clock_;
 };
 
 }  // namespace content
 
 #endif // CONTENT_BROWSER_MEDIA_SESSION_MEDIA_SESSION_UMA_HELPER_H_